JP-A-2001-060750 (corresponding to U.S. Pat. No. 6,377,468) discloses a relay module device in which a connecter terminal is joined to a circuit substrate, such as a printed circuit board including elements and an electrical circuit for forming a relay, and the connecter terminal is pulled out to the outside of a casing including a connector housing so that the connecter terminal can be electrically connected with an external device.
In cases where the number of loads switched by the relay (hereafter, referred to as load number) and an electric current supplied to the loads (hereafter, referred to as load currents) are different, the circuit substrate, the connector housing, the connector terminal, and the casing in the relay module device are generally changed. In other words, in cases where the load number and the load currents are different, a different circuit substrate, a different connector housing, a different connector terminal, and a different casing are prepared.
However, new components need to be prepared for each kind of device in accordance with the load number and the load currents. Thus, a layout design of the circuit substrate and molding tools for the connector housing and the casing are required for each kind of device, and increase in manufacturing cost is caused. In addition, if a wiring pattern of the electrical circuit included in the circuit substrate is changed, influence on a vehicle noise (emission and immunity) is changed. Thus, even in cases where the same electronic components are mounted, an evaluation test similar to a new product is required, and a time and a cost for product development increase. Therefore, it is desired to commonize a circuit substrate in plural kinds of relay module devices having different load numbers and different electric currents.